1. Field of the Invention
This invention relates to field subassemblies for electric motor-powered devices, including power tools, and a method for assembling the field subassemblies. In particular this invention relates to a field subassembly in which subassembly elements such as insulating members or coil supports are aligned in a predetermined orientation with a ferromagnetic core by fasteners which are pushed, instead of threaded, into the subassembly elements. With the fasteners in place, and after the field has been wound, a brush holder subassembly is pressed onto the fasteners yielding a core subassembly; the entire core subassembly is then attached to the field housing using the same fasteners.
2. Description of The Prior Art
When it is desired to provide a coil support for the core of a field so that adjacent windings of field coil wire are supported during the winding operation, it is necessary that the coil supports be maintained in a predetermined relation to the core. Among the systems used to maintain the coil support in this predetermined relation are those which use a coil support having a plurality of holes formed therein corresponding to the holes used to align the laminations in the stack forming the core. In such a system, bolts are inserted in a conventional manner through the holes in the coil support and through the stack alignment holes, and the core is subsequently wound with field coil wire. Another system uses projections extending outwardly from the core-engaging face of a coil support to engage holes in the ferromagnetic core. Then the field is wound with the field coil wire; bolts or other fasteners are inserted into the core, and the subassembly is subsequently connected to a housing.
A third system uses bolts inserted in a conventional (rotating) manner into the openings formed in the pads in a motor housing and through the respective through-openings in the stacks of laminations. The bolts, however, are not inserted until after the field has been wound, and no coil supports are attached.
It can therefore be seen that up to the present, a set of fasteners has been used either in the early stages of the field assembly process or at the final stages; but the same set has not been carried with the field stack throughout the entire subassembly process. Thus at least two sets of fasteners are inserted and locked in place, thereby requiring that at least one set be totally removed from the subassembly during the process. The present invention bridges that gap by using the same set of fasteners throughout the entire process, ultimately including the step of attaching the core to a mounting member. Thus the middle steps of removal and replacement of at least one set of fasteners are eliminated. Furthermore, the present invention permits an insulating member such as coil support to double as a female fastener member, in that the fasteners are pushed, not rotated, into engagement with the coil support with a press-fit, thereby locking the fasteners in place.